Wind tunnel study of gaseous pollutants in city street canyons
Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Velues of concentration measured in the model city were converted to prototype concentrations in ppM and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometrics for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions.
- Research Organization:
- Colorado State Univ., Ft. Collins
- OSTI ID:
- 5337064
- Journal Information:
- J. Air Pollut. Control Assoc.; (United States), Journal Name: J. Air Pollut. Control Assoc.; (United States) Vol. 27:6; ISSN JPCAA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Atmospheric-- Basic Studies-- (-1989)
500200 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
AIR QUALITY
BUILDINGS
DILUTION
FLUIDS
GASES
HUMAN POPULATIONS
MATHEMATICAL MODELS
POLLUTION
POPULATIONS
ROADS
SIMULATION
STANDARDS
TUNNELS
URBAN AREAS
URBAN POPULATIONS
VEHICLES
WIND TUNNELS